From DE 198 04 053 A1 a lightweight construction valve for an internal combustion engine with a ratio of wall thickness to stem diameter of less than 1:3 is known. This is to minimise a deformation of the valve head. According to an embodiment, a valve cone in this case is formed unitarily welded to a valve stem and according to another embodiment welded to the valve stem via a welded connection.
From DE 10 2004 010 309 A1 a further hollow valve with a hollow valve stem and a valve disc is known, wherein a valve cone is welded to the valve stem and to the valve bottom.
In order to satisfy steadily rising safety requirements it is also necessary with built hollow valves to create a testing surface located at the transition of the valve cone to the valve stem, via which the built hollow valve for example can be subjected to a quality test by means of ultrasound. The testing surface on the one hand has to be smooth and on the other hand so large that a weld seam depth can be entirely covered. When welding-together the valve cone and the valve stem merely an uneven weld seam course can be achieved up to now, which does not make possible reliable and reproducible testing of the weld seam or only under very difficult conditions so.